Method and apparatus for protection of power humidifier



A. YURDIN Feb. 24, 1970 METHOD AND APPARATUS FOR PROTECTION OF POWER HUMIDIFIER Filed July 25, 1967 "I2 a??? :graft:

""fc "rp EVAPORATOR PAD IMPREGNATED/ FUER INVENTOR EYmm m P ATTORNEYS.

United States Patent O Int. Cl. C02b 1/22 U.S. Cl. 210-58 15 Claims ABSTRACT F THE DISCLOSURE This specification discloses a method and apparatus for preventing the burning out of motors on power humidifiers and the clogging of the evaporator pads as the result of min-eral deposits inside the recirculating pumps and in the interstices of the evaporator pads. Where hard water is likely to cause these results, this invention recirculates with the water in the humidifier chelating and coating agents that keep minerals, which crystallize in the water, free-flowing; and that coat the particles. Filters remove the coated particles from the closed system to limit the viscosity of the recirculating mixture. In the preferred constructions, there are several different arrangements of apparatus for filtering either the full fiow or a by-passed flow, the latter permitting continued operation of the humidifier even though the filter is so filled with mineral deposits as to interfere with further flow of water through the filter.

BRIEF DESCRIPTION OF THE INVENTION An eicient and popular type of power humidifier has a motor-driven pump that delivers water from a sump to an evaporator pad through which air is moved by a fan. Excess water drops from the pad back into the sump and is recirculated by the pump. In hard-water localities, where evaporation of Water increases the concentration of minerals above the saturation point, the minerals coat the inside of the circulating pump and clog the interstices of the evaporator pad in less than one season of operation. o

The building of the coating in the pump causes increased friction in the pump and often burns out the mo tor. The clogging of the evaporator pad reduces the efficiency of the humidifier, and pads have to be replaced after very short periods of use.

This invention prevents coating of the inside of pumps and prevents buildup of `mineral deposits in the evaporator pad by keeping the minerals that crystallize from the water in a free-flowing condition. In the preferred embodiment of the invention, the free-owing crystals are caught in filters so as to prevent a buildup of the viscosity of the recirculating mixture of water and suspended solids. This is done by circulating chelating and suspending agents simultaneously with the water through the humidifier circuit.

Although chelating agents for keeping crystals in suspension in a mother liquor are known and have been used in certain chemical processes, they have not been used in methods for protecting the pump and evaporator pad of a power humidifier.

The invention also includes several arrangements of apparatus for filtering either the full stream or a bypassed stream of the recirculating mixture of water and suspended solids. Apparatus for full stream filters is somewhat simpler in construction, lbut the use of a bypass system has the advantage that even though the apparatus does not get adequate maintenance care and the filter becomes clogged, the humidifier can continue to operate though at decreasing efficiency.

ICC

lOther objects, features and advantages of the invention will appear or be pointed out as the description proceeds.

DETAILED DESCRIPTION OF THE DRAWING In the drawing, forming a part hereof, in which like reference characters indicate corresponding parts in all the views:

FIGURE 1 is a diagrammatic sectional view through a power humidifier having a pump for supplying water to an evaporator pad;

FIG. 2 is a diagrammatic exploded view of a portion of the apparatus in the humidifier of FIGURE l;

FIGURE 3 is an isometric view of one of the filters shown in FIGURE 2;

FIGURE 4 is a sectional view on the line 4 4 of FIG- URE 1;

FIGURE 5 is a diagrammatic sectional view showing another type of power humidifier;

FIGURE 6 is a sectional view taken on the line 6 6 of FIGURE 5;

FIGURE 7 is a sectional View through a different typ; of filter from those shown in FIGURES 1 and 2; an

FIGURES 8 and 9 are diagrammatic piping diagrams showing the way in which the filter of FIGURE 7 can be used as either a full-flow or by-pass ow filter with the humidifier shown in FIGURE l.

DETAILED DESCRIPTION OF THE INVENTION The humidifer shown in FIGURES 1-4 includes an evaporator pad 10 to which water is supplied from a tray 12 located on top of the pad 10. The tray 12 has openings in its bottom through which water runs down into the evaporator pad 10. In the construction illustrated there is a filter 14 located between the tray 12 and the pad 10. There is another filter 16 under the evaporator pad 10 and a dished bafiie 18 with a center outlet 20 `catches all of the excess water that runs through the pad 10. A sump or water reservoir 22 is located under the baffle 18 and water runs through the center outlet 20 into the reservoir 22. The reservoir has an overflow 24.

Water which runs into the reservoir 22 from the outlet 20 is recirculated by a pump 28 driven by a motor 30.

The discharge from the pump 28 is connected with tubing 34 which leads to the top of the humidifier and which discharges into the tray 12. Since substantial quantities of water are lost by evaporation, it is necessary to supply makeup water. This is done by a water supply pipe 36 having a valve 38 operated -by a fioat 40 in the reservoir 22.

When the water level in the reservoir 22 drops below a given level, the float 40 drops and opens the valve 38. As the water level rises, the float 40 also rises and closes the valve 38. So long as the valve 38 is operated by the fioat 40, the level of water in the reservoir never reaches the height of the overflow 24; but in the event of improper operation of the valve 38, the overflow of water through the overflow 24 provides a warning that the humidifier needs attention.

There is a fan 46 behind the evaporator pad 10 and this fan is driven in a direction to draw air through the pad. In the construction shown in FIGURE 4, the humidified air is discharged from a chamber 48 behind the fan through louvres 50 in the wall of a housing 52 of the humidifier.

In order to prevent minerals from coating the inside of the pump, and the interstices of the evaporator pad 10, chelating and supending agents are introduced into the Water which is recirculated in the humidifier. The agents which are preferably used for the pump are EDTA (ethylenediamine tetra-acetic acid) and quebracho. The che- Patented Feb. 24, 197D [ating or sequestrating effect of the EDTA is to nullify the undesirable effects of metal ion impurities in the water. By combining with bi, or tri, polyvalent metal ions in the aqueous system, the EDTA forms complexes with the calcium, iron, copper, magnesium, tin and other metal ions present in hard water. The quebracho acts as a buffer and suspending agent by forming a protective coating around the solids which crystallize out of the water as the concentration exceeds the saturation point for the various solids.

This keeps the solids free-fiowing as suspended in the water and prevents the coating of the inside of the pump and the interstices of the evaporator pad. However, the evaporator pad, if the interstices are small enough, may become clogged by filtering out the suspended solids. To prevent this, and to limit the viscosity of the recirculating mixture, the filters 14 and 16 are put at the top and bottom of the evaporator pad. Either of these filters 14 or 16 can be used alone. The filters 14 and 16 are replaced from time to time, and the period of operation before replacement depends, of course, upon the hardness of the water and the quantity of water evaporated by the humidifier.

In the preferred embodiment of the invention, the EDTA and quebracho (or its equivalent) are not used alone. Benzotriazole in a small amount is used as an inhibitor to prevent the EDTA from causing deterioration of any copper or aluminum of the humidifier. Better results are obtained by using a dispersing agent in the mixture and it is also desirable to include a rust inhibitor. The preferred mixture of chemical reagents includes also a quaternary ammonium compound for algae control.

When the formulation is supplied as a tablet, a binder is included in the formulation to hold the tablet together. The preferred formulation, in addition to the chelating or sequestering agent and the buffer referred to above, includes sodium nitrite as the rust inhibitor and a polyelectrolyte (Disperse A-6) as the dispersing agent. Benzotriazole is used as the inhibitor for the EDTA against damage to copper and aulminum. Magnesium stearate may be used as the binder for the tablet.

An illustrative formula which gives very good results contains the following proportions of ingredients by weight: 50% EDTA; 35% quebracho; 81/2% sodium nitrite; 31/2% Disperse A-6; 1% benzotriazole; .5% quaternary ammonium compound; and 11/2 magnesium stearate.

Although the preferred formulation obtains remarkable results, some changes in the proportions can be made with out unduly restricting the results obtained. For example the amount of EDTA can be varied between about 45 to 70%. The quebracho can be varied between about 25 to 40%.

The amount of the rust inhibitor can be Varied between about to 10%; the dispersing agent between about 3 to 5%. The benzotriazole can be varied from about .5 to 1.5%; and the algae control from about .25 to 1%.

Substitutions can be made for the different active ingredients. In the place of the EDTA (which is preferably used in the form of a tetrasodium salt), nitriloacetic acid trisodium salt monohydrate can be used. Tannic acid can be used in place or the quebracho; and sodium benzoate can be substituted for the sodium nitrite.

In place of benzotriazole, sodium gluconate can be used, or sodium silicate. Tributyl tin chloride is a substitute for the algae control. Various substitutes can be used for the binder such as calcium stearate with the necessary mold release, for example, hydrogenated cocoa oil.

The successful operation of the invention for protecting a power humidifier from damage by hard water and particularly for protecting the motor that drives the pump, depends upon there always being sufficient quantity of the formulation in the circulating system. Since the most important ingredients of the formulation are used up as additional minerals are precipitated from the water,

it is necessary to add quantities of the formulation from time to time. The most convenient time to do this is when replacing a filter.

It is a feature of the invention that additional formulation is needed only when filters are replaced; and it is another feature of the invention that a service man can not forget to add the formulation in the right quantity whenever he replaces a filter.

In the preferred embodiment of this invention, the formulation is placed on the filter pad, either by impregnating it in the pad or assembling a tablet 58 (FIG- URE 3) of the formulation with the filter by means of a tape 60. When a service man finishes servicing a humidier, he never has any doubt about whether he has replaced the filter because he has the old filter which has been replaced, but unless the formulation is a unit with the filter, it is very easy for a service man to forget to put the formulation in the humidifier and when he finishes the servicing he has no easy check whether he did or did not insert the new formulation.

An important reason for making a filter and the formulation as a unit, however, is to insure the right amount of formulation to protect the humidifier until it is necessary again to replace the filter. The amount of formulation used up in a humidifier depends upon the hardness of the water at each location and the filling up of the filter also depends upon the hardness of the water. This invention correlates the formulation with the capacity of the filter so that there is enough of the formulation with each filter to treat as much solid material from the water as will fill up that particular filter.

For a particular service organization in a particular territory, a filter may be considered filled up when its resistance to fiow has increased or some other specified amount beyond which the efficiency of the humidifier is considered unsatisfactory. Such specially made filter-formulation combinations have the advantage that they do not use unnecessary amounts of the formulation and are, therefore, more economical; but where it is desirable to have a standardized filter-formulation combination for all of the humidifier service organizations in a locality, the filter is supplied with a quantity of formulation sufiicient to treat enough water to fill up the filter to the extent that any competent service man would consider it in need of replacement. For purposes of this invention, the formulation is enough to treat a quantity of water which will fill up the filter to a flow-resistance increase of at least 50% and preferably between 50% and FIGURES 5 and 6 show a modified form of the invention in which the water is not recirculated by a pump. The humidifier includes a housing 64 having a reservoir 66 in which the water is contained. An evaporator pad 68 is wrapped around a drum 70' having an axle 72 which rotates in bearings 74 at opposite sides of the housing 64.

The drum 70 is rotated by a motor 78 having reduction gearing 80 which drives a belt 82 that passes around a pulley 84 0n the axle 72.

The drum 70l has spokes with space between them through which air can enter the drum, as indicated by the arrows 88- in FIGURE 6. Air entering through one side of the housing 64 is deflected by louvres 90 toward an open end of the drum.

Other air enters the housing 64 through an end opening 92, as indicated by the arrows 94. The air flow is produced by a fan 96 located in a circular opening 98 in a partition across the inside of the housing 64. The fan 96 is driven by a motor 100 supported from one end of the housing 64. The humidified air exhausts from the housing 64 through openings 102 on opposite sides of the housing between the fan 96 and the end Wall which supports the motor 100.

The type of humidifier shown in FIGURES 5 and 6 is less desirable for use with this invention because such humidifiers do not include a pump for recirculating the liquid. To take full advantage of this invention it is necessary to add a pump 106 and a filter 108 located in a piping circuit 110 which constantly withdraws water from the reservoir 66 and circulates it through the filter 108.

In the operation of the humidifier shown in FIGURES 5 and 6, the minerals precipitated on the drum 70 wash off into the reservoir 66, into which the drum dips, because the chelating and coating agents prevent the minerals from caking on the evaporator pad 68 of the drum 70.

FIGURE 7 is a sectional view through the filter 108. This filter includes a container 116 with a cover, preferably a screwcap 120. An inlet pipe 122 and an outlet pipe 124 extend through the cover 120. There is an impregnated filter 126 located in the container 116 with some space for water both above and below the filter 126. The inlet pipe 122 reaches down through the lter and discharges water into a space 130 below the filter 126; and water which has passed upward through the filter is withdrawn from a space 132 through the outlet pipe 124.

FIGURES 8 and 9 show two different ways in which the filter of FIGURE 7 can be used on the humidifier shown in FIGURE 1. In FIGURE 8, the pipe 122 is connected with the pipe 34 as a branch passage for the liquid discharged from the pump 28. Some of the water passes through the pipe 34 to the evaporator pad in the humidifier and some of the water is by-passed through the pipe 122 to the filter 108. From the filter 108 the water fiows through the pipe 124 back to the reservoir 22.

FIGURE 9 shows a construction which differs from FIGURE 8 in that all of the water from the pump 28 is pumped through the pipe 122 to the filter 108. The entire discharge from the filter 108 passes through a pipe 34 to the evaporator pad of the humidifier. The construction shown in FIGURE 9 has the advantage that all of the water supplied to the evaporator pad is filtered before recahing the pad. The construction shown in FIGURE 8 has the advantage that the humidifier can continue to operate, though inefiiciently, even though the filter 108 becomes completely clogged.

It will be understood that the filter shown in FIGURE 7 is merely representative of means for filtering water which is circulated through the closed recirculating system of the humidifier, and that various other types of filters can be used. It is important, however, that the filters be of a type which can be easily replaced as necessary because power humidiers evaporate large quantities of water and substantial amounts of mineral deposits are precipitated in areas where the water is hard.

The filter provides a collecting station for the particles which are precipitated from the water. By coating the particles, in accordance with this invention, their removal from the system is facilitated and it is important that they be removed because the continued recirculation of the particles, as additional particles precipitate, eventually builds up the viscosity of the circulating mixture and overloads the motor which drives the pump.

When the humidifier is equipped with an evaporator pad having interstices or flow through passages, the filter is preferably made with small interstices so as to filter out particles of a size sufficient to clog the evaporator pad. Thus the evaporator pad is protected from clogging by having hard mineral deposits form along the flow passages so as to reduce the cross section and eventually clog them; and it is protected by withdrawing from circulation free-flowing coated particles which are large enough to clog the flow passages of the evaporator pad.

The preferred embodiments of the invention have been illustrated and described and the invention is defined in the claims.

What is claimed is:

1. The method of protecting the pump and evaporator surface of a power humidifier from becoming coated with mineral deposits from hard water, which method comprises circulating and recirculating the water in the humidifier without substantial bleed-off of the circulating water from the humidifier, adding additional water to compensate the evaporation, recirculating with the water, and mixed therein, chelating and suspending agents that coat mineral particles which crystallize in the mixture whereby the crystallized minerals are kept free-fiowing with the water, collecting mineral particles at a collecting station by passing the circulating water and entrained mineral particles through a filter that traps and holds the coated crystallized mineral particles, and periodically replacing the filter to remove said particles from the collecting station and from the humidifier as necessary to prevent coating of the pump and evaporator surface and to keep the viscosity of the circulating mixture below a given value.

2. The method described in claim 1 applied to a humidifier that has an evaporator pad, which method is characterized by collecting coated minerals in the humidifier and adjacent to the pad, on a filter having flowthrough passages of smaller cross section than those of the evaporator pad, and removing accumulated particles by replacing the filter.

3. The method described in claim 2 characterized by distributing the water across the width of the pad at the top of the pad for flow into the pad by gravity, and loeating the filter across the width of the pad at the top of the pad and in the path of the water fiow to the pad.

4. The method described in claim 2 characterized by distributing the water across the width of the pad at the top of the pad for iiow into the pad 4by gravity, flowing through the pad more water than can be evaporated during the time of passage of the water down through the pad, collecting coated particles of minerals at the bottom of the pad by locating the filter across the width of the pad at the bottom thereof.

5. The method described in claim 1 characterized by collecting the water for recirculation in a space from which it is withdrawn by power means for return to the evaporator surface, and circulating at least part of the water through a filter by the same power means that are used to return water from the collecting space to the evaporator surface.

6. The method described in claim 1 characterized by collecting the water for recirculation at a space from which it is withdrawn by power means for return to the evaporator surface, and by-passing part of the water from the collecting space through a filter to collect in the filter particles of minerals that fiow to the filter in the water, and locating the filter in a space outside of the humidifier for more convenient access and replacement of filters.

7. The method described in claim 1 characterized by collecting the coated particles on a filter pad, replacing the chelating and suspending agents in the humidifier in proportion to their exhaustion from the system as coated particles are removed on filters, the proportional replacement being effected by securing to each new pad an amount of chelating and suspending agents sufiicient to coat a quantity of mineral particles that will fill the filter pad to a condition that requires replacement.

8. The combination of a formulation for protecting the pump and evaporator surface of a power humidifier from becoming coated with mineral deposits from hard water, which formulation comprises a chelating or sequestering agent, and a buffer or suspending agent that coats the particles precipitated from the water, and a filter element having interstices that will collect the particles chelated and coated by the formulation, the formulation being secured to the filter and comprising a unit assembly with the filter for insertion into a humidifier as original equipment or as replacement for a filled-up filter, the formulation being correlated with the capacity of the filter whereby the formulation will coat enough 7 particles to fill up the lter to a predetermined state at which the filter is to be replaced.

9. The formulation described in claim 8 characterized by the quantity of the formulation being sutiicient to treat enough Water to fill up the filter to an increased flow resistance of at least 50%.

10i. The formulation described in claim 9 characterized by the formulation comprising approximately 45 to 70% of a chelating agent, approximately 25-40% of buffer and suspending agent, approximately 5-10% of rust inhibitor, approximately 3-5% of an algae control and a binder.

11. The formulation described in claim 9 characterized by the formulation comprising 50% ethylenediamine tetraacetic acid, 35% q'uebracho, 81/2% sodium nitrite, 31/2% disperse (polyelectrolyte), 1% benzotriazole, .5% quaternary ammonium compound and 11/2% magnesium stearate.

l12. The formulation described in claim 9 characterized by the formulation including approximately 45-75% Of chelating or sequestering agent from the group consisting of ethylenediamine tetraacetic acid and nitrilotriacetate acid trisodium salt monohydrate, approximately 25-40% of buffer and suspending agent from the group consisting of quebracho and tannic acid, approximately 5-10% of rust inhibitor from the group consisting of sodium nitrite and sodium benzoate, and approximately 3-5% of an algae control from the group consisting of a quaternary ammonium compound and tributyl trichloride.

13. The combination With a power humidifier having a pump and evaporator pad, the evaporator pad having interstices therein through which water is circulated and recirculated by the pump without substantial bleed-off of the circulating Water from the humidifier, means for adding additional Water to compensate for losses caused by evaporation of Water from the pad, means for protecting the pump and evaporator pad from Ibecoming coated with mineral deposits from hard Water, including chelating and suspending agents in the recirculating system of the humidifier that coat mineral deposits which crystallize in the mixture whereby the crystallized minerals are kept free-flowing with the Water, a collecting station including a Iilter through which the recirculated Water passes, the filter having a fineness that is coordinated with the size of the interstices of the evaporator pad for removing coated particles which are entrained in the recirculating Water and which are large enough to clog the interstices of the evaporator pad, the Iiilter being removable from the humidifier system for periodic replacement to remove the particles from the collecting station and from the humidifier as necessary to prevent coating of the pump and evaporator pad and to keep the viscosity of the circulating mixture below a given value.

14. The combination described in claim 13 characterized by the filter being in series with the evaporator pad in the recirculation system and all of the Water that passes through the evaporator pad passing through the filter.

15. The combination described in claim 13 characterized by the filter being located outside of the humidifier and being in a by-pass of a portion of the recirculation system but supplied with liquid from the humidier by the same pump that recirculates the liquid to the evaporator pad.

References Cited UNITED STATES PATENTS 2,319,565 5/ 1943 Stratton 261-97 X 2,631,021 3/1953 Arnold 261-97 X 3,043,772 7/1962 lLiddell 210-57 3,126,427 3/1964 Broughton 210-57 X 3,173,864 3/1965 Freedman 210-57 3,191,915 6/1965 Goettl 261-97 3,228,665 1/1966 Dolan 261-97 X 3,332,871 7/1967 Robinson 210-58 X 3,412,021 11/1968 Patterson 210-62 FOREIGN PATENTS 967,086 8/ 1964 Great Britain.

OTHER REFERENCES Betz: Handbook of Industrial Water Conditioning, fth edit., 1957, pp. 96, 97, 98, 148-151, 157, 172, 173 and 184-186 relied on, Betz Laboratories, Inc., Phila., 24, Pa.

MICHAEL E. ROGERS, Primary Examiner U.S. Cl. X.R. 

